Tobacco smoke filter having a coated carbon additive



United States Patent Oflice 3,426,763 Patented Feb. 11, 1969 3,426,763TOBACCO SMOKE FILTER HAVING A COATED CARBON ADDITIVE Cephas H. Sloan andBobby J. Sublett, Kingsport, Tenn., assignors to Eastman Kodak Company,Rochester, N.Y., a corporation of New Jersey No Drawing.Continuation-impart of application Ser. No. 447,093, Apr. 9, 1965. Thisapplication July 21, 1965, Ser. No. 473,809 US. Cl. 131-266 2 ClaimsInt. Cl. A24d 1/06; B01d 27/02 ABSTRACT OF THE DISCLOSURE A new filterfor tobacco smoke in which hydrogen cyanide is effectively removedcomprises a core or carrier of continuous cellulose acetate filamentswhich carry as an addition thereon a nonactivated carbon coated with awater soluble salt. Sodium carbonate, potassium carbonate, sodiumphosphite, potassium phosphite, sodium phosphate, potassium phosphate,sodium silicate, and potassium silicate constitute the effective watersoluble salts. The nonactivated carbon base does not absorb volatiletaste producing vapors to the extent that the activated carbons do.

This is a continuation-in-part of our copending application Ser. No.447,093, filed Apr. 9, 1965.

This invention relates to .a tobacco smoke filtering material forselectively removing deleterious materials from tobacco smoke withoutremoving the desirable smoke vapors which contribute aroma and taste tothe smoke. More particularly, this invention concerns a novel cigarettefilter tow and filter made therefrom as well as the method for theirmanufacture. The invention further pertains to a specially coated carbonpowder additive for selectively removing certain deleterious materialsfrom tobacco smoke.

In our US. patent application Ser. No. 425,920, filed Ian. 15, 1965, wedisclose that the use of certain watersoluble inorganic salts willremove substantial amounts of hydrogen cyanide from tobacco smoke. Whilesuch salts have proven to be highly successful hydrogen cyanide removalagents, we have noticed in some instances a tendency of these additivesto dust off the filter tow during processing and that they are difiicultto distribute uniformly over the surface of the tow. Thus, in suchinstances difiiculty in making a uniformly coated tow and tobacco smokefilters from the tow has been experienced. Therefore, both thedevelopment and manufacture of a tobacco smoke filter element withimproved hydrogen cyanide filtration efiiciency represents a highlydesirable result.

After extended investigation we developed various novel additives for atobacco smoke filter which are described and claimed in our copendingapplication Ser. No. 447,093, filed Apr. 9, 1965, of which this is acontinuation-in-part. However, it has now been found that another noveladditive for removing substantial amounts of hydrogen cyanide fromtobacco smoke can be produced from relatively inexpensive components.

Therefore, one object of this invention is to provide a new and improvedtype of tobacco smoke filter element. Another object is to provide anadditive which may be applied to cigarette filter tow to selectivelyremove hydrogen cyanide (HCN) from the vapor phase of tobacco smoke. Afurther object is to provide a method for making an improved tobaccosmoke filter. Still another object is to provide an improved additivefor use with a cellulose acetate filter tow.

In its broader aspects our invention involves adding to a tobacco smokefilter carbon powders or granules which have water-soluble inorganicsalts coated on the surface thereof, especially the salts of Group Iaelements of the Periodic Table. Inorganic salts which we have foundparticularly useful according to our invention include the sodium andpotassium carbonates, phosphites, phosphates, and silicates, or mixturesof these. The salts are coated on the carbon particles by adding aweighed amount of the particles to an aqueous solution of one or more ofthe aforementioned salts. The inorganic salt solution should contain asufficient concentration of the salt so that after the water is removedthe carbon powder will have deposited on its surface 20 to 40 percentsalt by weight. The concentration of salt in solution can be carried togive the desired amount of salt deposit on the carbon. The coated carbonparticles are normally carried on a fibrous type filter medium and maybe applied thereto by a vibrating device. However, any other suitablemethod of evenly dispersing a dry powder or granular material onto afilter tow may be employed. The amount of carbon additive coated withsalt that may be added to a filter tow according to our invention isbetween 10 and 30 percent based on the weight of the tobacco smokefilter.

Although activated carbon particles can be used as the carrier materialfor a salt additive, it has been found that such carbon particles havecertain disadvantages. Besides the fact that such activated carbonparticles are rather expensive to produce, they are also nonselective inthe vapors they absorb. In general, activated carbon absorbs vaporsaccording to their boiling points. Hence, the least volatile vapors willbe absorbed and retained more readily than the lower boiling vapors. Wehave found that certain types of carbon, such as that used indecolorizing and pigmentation work (nonactivated carbon), which havelittle or no afiinity for tobacco smoke makes a superior carrier forsalt additives, and that such salt coated carbon particles when used ina tobacco smoke filter produces .a superior selective filter unit. Thesenonactivated carbon powders are superior carriers for the inorganicsalts since they 1) will not absorb those nondeleterious volatile vaporswhich give taste to the tobacco smoke, and (2) are relativelyinexpensive to produce.

According to one embodiment of the instant invention a crimped tow isspread out to a width of approximately 15 inches as it moves through acigarette filter-making machine. A vibrating pan adapted to coat thesurface of the tow is placed directly above and parallel to the tow. Inthe pan is placed a nonactivated carbon powder which will pass through aZO-mesh screen and coated with an inorganic salt. The coating of thenonactivated carbon particles is performed by placing, for example, 6grams of the particles into 20 ml. of aqueous solution containing 4grams of a dissolved inorganic salt selected from the group includingsodium and potassium carbonates, phosphites, phosphates, and silicates,or mixtures of these. After the nonactivated carbon particles havesoaked for a reasonable period of time they are taken from the saltsolution and the water remaining in the particles is removed byevaporation thus leaving a dry carbon powder coated with a 40 percentsalt coating, based on the dry weight of the powder. The vibrator pan isadjusted to apply the desired amount of additive, and the additive isvibrated onto the filter tow as it moves throuugh the filter-makingequipment. If desirable, an adhesive or plasticizer can be added to thetow prior to the addition of the carbon coated additive. As the towcontaining the additive moves through the filter-making equipment, thetow is formed into a continuous cylindrical rod and wrapped in paper.This paper encased cylindrical rod may be cut into any desired lengthand used either alone as a filter unit or in combination with otherfilter units to make a dual or multiple tobacco smoke filter. While thesalt coated carbon particles may be added to the tow as described above,cigarette filters may also be made by positioning a coated carbon massbetween filter cylinders made of filaments by methods known in the art.

A further understanding of the invention will be had from aconsideration of the following examples which are set forth toillustrate certain preferred embodiments.

Example I A l70-mm. length of 5 denier/filament (d./f.) crimpedcellulose acetate filter tow which had 9,000 filments and weighedapproximately 1 gram was spread out to a width of 15 inches. Glyceryltriacetate (triacetin) in the amount of 9 percent by weight of the towwas applied to the tow by rollers. A dry nonactivated carbon powderwhich contained 40 percent by weight of potassium acid carbonate coatedon its surface was applied to the tow from a vibrating pan until 30percent, based on the dry weight of the tow, had been added. The tow wasformed into a cylindrical rod, wrapped with a paper tape and allowed tostand until it became firm. The cylindrical rod thus formed, which has acircumference equal to a standard domestic cigarette (25 mm.), was thencut into 20-min. segments. The 20-min segments, which containedapproximately 30 mg. of coated carbon, were attached to king-sizecigarettes by means of a cellophane tape. The cigarettes were smokedwith an automatic smoking device, and the vapors which passed throughthe filter were collected and analyzed spectrophotometrically and by gaschromatography. These values are recorded in Table 1 below. Alsorecorded in Table 1 are the amounts of these vapors obtained from thesame type filter element containing an untreated nonactivated carbonadditive.

TABLE 1 g. found in smoke pg. found in smoke from one cigarette As willbe noted from Table l, the salt coated nonactivated carbon filter ismuch more effective in selectively removing the vapors of hydrogencyanide from tobacco smoke.

ExampleH A 170-mm. length of 5 d./f. crimped cellulose acetate filtertow which had 9,000 filaments and weighed approximately 1 gram wasspread out to a width of 15 inches. Glyceryl triacetate in the amount of9 percent by weight of the tow was sprayed onto the tow. Drynonactivated carbon granules which contained 30 percent sodium silicateby weight coated on its surface was uniformly applied to the tow from avibrating pan until 20 percent total additive, based on the dry weightof the tow, had been added. The tow was formed into a cylindrical rodand wrapped with a paper tape to form a rod. The rod was allowed tobecome firm and then was cut into 20-min. segments. The 20-mm. segmentswere attached to king-size cigarettes by means of a cellophane tape andthe cigarettes smoked with an automatic smoking device. The vapors whichpassed through the filter were collected and analyzedspectrophotometrically and by gas chromatography. The amount of hydrogencyanide and certain other vapor phase components which passed throughthe filter are shown in Table 2. Also shown in Table 2 are the vaporswhich passed through the same type 'filter elements containing an amountof activated carbon equivalent to that of the treated carbon which wassmoked and analyzed in a similar manner.

TABLE 2 pg. Found in smoke from one pg. Found in smoke from one Itshould be noted that the filter containing the nonactivated coatedcarbon additive is highly selective in the vapor it removes, and thatsome of the volatile vapors which give the desired taste and flavor tothe tobacco smoke were permitted to pass in large quantities.

Example III A 170-mm. length of 5 d./ f. crimped cellulose acetatefilter tow which had 9,000 filaments and weighed approximately 1 gramwas spread out to a width of 15 inches. Glyceryl triacetate in theamount of 9 percent by weight of the tow was sprayed uniformly over thesurface of the tow. Treated nonactivated carbon granulars (20 X 50 mesh)containing 20 percent sodium acid carbonate on their surfaces weredusted on the thus treated tow from a vibrating pan until 30 percent ofthe additive, based on the dry weight of the tow, had been added. Thetow was then formed into a cylindrical rod and wrapped with paper toform a filter rod with a circumference equal to that of a standardcommercial cigarette. The rod was allowed to stand until it became rigidand then was cut into 20-min. segments. The 20-mm. segments or filterelements, which contained approximately 30 mg. of treated carbon, wereattached to king-size cigarettes by means of a cellophane tape and thecigarettes smoked with an automatic smoking device. The vapors passingthrough the filter were collected and analyzed spectrophotometricallyfor hydrogen cyanide. The amount of hydrogen cyanide found was 35 ,ug.The amount of hydrogen cyanide found by similarly analyzing a king-sizecigarette with a plain cellulose acetate filter containing no treatedcarbon was 225 g. From this it can be seen that the hydrogen cyanidecontent of the tobacco smoke which passes through a filter containingthe salt coated nonactivated carbon additive is reduced by over percentfrom that which is permitted to pass through a fibrous filter unitcontaining no such additive.

From the foregoing description it is readily apparent that the coatedcarbon additive of this invention offers numerous advantages over thosepreviously known. Not only is carbon of the nonactivated type anexcellent carrier medium, but it is both inexpensive to produce and canbe handled by existing filter forming equipment. Furthermore, thenonactivated carbon does not remove any of the highly volatile vaporswhich gives the desired flavor to tobacco smoke as would occur if anactivated material like activated carbon were used as the carriermedium.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are, therefore, to be considered in all respects asillustrative and not restrictive.

What is claimed and desired to be secured by United States LettersPatent is:

1. A vapor-permeable rod-shaped element comprising a core of compactedsubstantially horizontally aligned cellulose acetate filaments containedin a close-fitting wrapper, said filaments containing as a tar andhydrogen cyanide removing additive 10 to 30 percent by weight of saidelement of nonactivated carbon granules coated with 5 20 to 40 percentby weight of a water-soluble inorganic salt selected from the groupconsisting of sodium carbonate, potassium carbonate, sodium phosphite,potassium phosphite, sodium phosphate, potassium phosphate, so-

dium silicate, and potassium silicate.

2. A tow adapted for being formed into a tobacco smoke filter comprisinga continuous cellulose acetate carrier medium having as an additivethereon nonactivated carbon particles coated with at least oneWatersoluble inorganic salt selected from the group consisting of sodiumcarbonate, potassium carbonate, sodium phosphite, potassium phosphite,sodium phosphate, potassium phosphate, sodium silicate, and potassiumsilicate.

References Cited UNITED STATES PATENTS 2,172,946 9/1935 Sutter 1312652,815,760 10/1957 Schrens et a1 131262 X 8/1963 Seligman et al. 1312664/1959 Tovey 131266 5/1966 Keith et a1. 131-10.9 X 10/1967 Lloyd 1312665/1967 Hughes et a1. 13l-267 9/1958 Spaulding et a1. 256-446 2/1968Avedekian 1319 X FOREIGN PATENTS 10/ 1930 Great Britain. 11/ 1956 GreatBritain.

US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,426,763 February 11, 1969 Cephas H. Sloan et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 4, line 70, after "element" insert useable as a tobacco smokefilter Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR.

